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I have seen these terms being used almost interchangebly, but are decomposition and dissociation reactions the same ?

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    $\begingroup$ I would say they are different because I wouldn't say an acid dissociating in to its ions (in an aqueous solution) is the decomposition of the acid. However I may be proven otherwise. $\endgroup$
    – LiamH
    Aug 10, 2015 at 10:11
  • $\begingroup$ Could you give us some of those examples that you mention? $\endgroup$ Aug 10, 2015 at 12:50

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Decomposition and disassociation refer to similar processes, however they are different. The main difference between them is that decomposition reactions are usually irreversible while disassociation reactions are reversible and exist in equilibrium.

A decomposition reaction is where a compound breaks up into smaller elements or compounds. For example: $$\ce{2H2O -> 2H2 + O2}$$ is an example of a decomposition reaction. Note that in this case that this is actually a reversible reaction.

A disassociation reaction is the general process where molecules split into smaller particles which can include elements, compounds, ions and radicals. For example: $$\ce{NaCl(s) -> Na+ (aq) + Cl- (aq)}$$ is a disassociation reaction.

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  • $\begingroup$ they partially overlap - decomposition can proceed via dissotiation $\endgroup$
    – Mithoron
    Aug 10, 2015 at 18:22
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    $\begingroup$ Your example of a "decomposition" reaction is not very "irreversible", in fact the opposite: the reverse reaction (hydrogen combustion) that is irreversible. It isn't really accurate to classify reactions by their reversibility. $\endgroup$
    – Curt F.
    Aug 11, 2015 at 2:02
  • $\begingroup$ Thanks for pointing that out. I have edited my answer now. $\endgroup$
    – Nanoputian
    Aug 11, 2015 at 6:55

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